Technical Field
The invention relates to a method for manufacturing a touch sensing device and to a touch sensing device.
Background Art
In the manufacture of a touch sensing device including an optical film laminate, a touch-panel maker normally obtains a material film for producing optical film laminates in the following way. First, a PET-film maker forms and then biaxially stretches a PET (polyethylene terephthalate) film having a width of several meters using an extrusion machine, divides the PET film into a plurality of parts in a widthwise direction (transverse direction, TD), and ships the divided PET films to an ITO-film maker. Next, an ITO-film maker forms an ITO film on a face of each divided PET film, and further divides each divided PET film into a plurality of parts in a widthwise direction. Each divided PET film with an ITO film is shipped to a touch-panel maker and serves as a material film for an optical film laminate.
A touch-panel maker uses such material film to form a plurality of electrode groups on a face of the material film, and cuts the film into a plurality of portions, each with an electrode group forming a substrate. Then, a touch-panel maker bonds two substrates together to make an optical film laminate for a touch sensing device.
It is preferable that the two substrates have respective fast axes that are substantially parallel to each other, for the purpose of e.g. improving visibility of visual information when seen through a polarizing plate such as polarizing sunglasses. However, it is difficult under conventional manufacturing methods to mass-produce optical film laminates each including two substrates having fast axes that are substantially parallel to each other. Particularly, as material films for producing optical film laminates are obtained by dividing a biaxially-stretched PET film into a plurality of parts in the widthwise direction, their fast axes extend at totally different directions from one material film to another. Accordingly, if two substrates are obtained from different material films, their respective fast axes extend in significantly different directions from each other. Therefore, it is extremely difficult to bond two substrates such that their respective fast axes are substantially parallel to each other, without previously determining the fast axes.
JP 2006-56117 A discloses another conventional method for manufacturing a touch sensing device. This method addresses a problem of reducing curling of an optical film laminate when heated, by cutting two adjacent areas in the widthwise direction out of a biaxially-stretched material film to make two substrates and bonding the substrates in symmetric arrangement. As a result, the two substrates have substantially the same thickness, and the difference of the optical axis orientation between the two substrates is within a range of 20° or smaller.